Building a Vault?

Coming up with an idea and I'll try my best to explain it.

I have a house with an unfinished basement with an 8" poured concrete wall. I am toying with the idea of cutting an opening for a vault door in the basement wall and making an "underground" vault beneath my garage floor. I am hoping to make the room 10x10. With a concrete roof (garage floor) and a fireproof vault door and it being undergound and beneath the garage, it would be completely fireproof and waterproof.

My question is how much can I excavate under the garage floor before it needs to be reinforced? Obviously the floor of the garage needs to be strong enough to support vehicles (4" fiber reinforced floor), but do I need to use I-beams or will timbers work?

I plan on digging down a ways so I can attach rebar to the existing footer and pour a slab inside the room as well. So we would have a concrete floor, 3 sides of dirt and one side with a vault door and the existing basement wall.

Any and all info is appreciated. Thanks

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Building a Vault?

Disclaimer-I'm not an engineer or contractor of any kind-but...

I would think that going under the garage would prove to be too complicated and costly. Concrete slabs not resting on solid earth typically are either poured on top of corrugated metal underlayment that helps stiffen them up a lot with a TON of re-bar/re-wire in the slab itself. Not to mention the fact that you need the concrete to support its own weight plus the weight of a vehicle. A 15' x 10' x 4" slab is going to weigh 7500lbs plus say at least another 4000. That's nearly 12,000lbs right there. You'd need some pretty beefy support beams and I'm betting there's no way to reinforce the slab that's already there.

Why not excavate an area on one of the other exterior walls, cut a doorway, and pour some walls/a roof around it, then cover it with dirt? You might even be able to buy some kind of pre-cast vault (like the ones for storm drains, etc...) and modify it. Either way I bet that it would be cheaper than hiring an engineer to try and retrofit your old slab. In any event, let us know what you come up with because I have a similar idea that I'd like to implement when I build my own home one day. I'd like to have a decent size room (10x12) if possible so that I could keep all of my guns/ammunition stored there plus have a reloading/smithing bench where I could leave things like gunpowder/guns laying around and simply close the vault door when I leave.

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Building a Vault?

You can easily have a contractor quickly saw the new opening in the basement wall. Make sure you have enough strength left to carry the loads from the house walls and floors above.

You cannot count on the fiber reinforced concrete for stuctural purposes. It is not a replacement for rebar.

If you feel you need the vault, it would be best to saw and remove the garage slab. Then, replace with a slab designed for the pupose. That way, you could have a clean installation with no supporting beams and columns. It will also give you an opportunity to backfill and compact behind your new vault walls. After backfilling, pour any remaining areas of garage floor that need to be finished.

Obviously, you will need an engineer to check the portions left and to size anything new.

Building a Vault?

Quote:

My question is how much can I excavate under the garage floor before it needs to be reinforced? Obviously the floor of the garage needs to be strong enough to support vehicles (4" fiber reinforced floor), So we would have a concrete floor, 3 sides of dirt and one side with a vault door and the existing basement wall.

Ayuh,.... The reinforcing, shoring should start as Soon as you get to the other side of that 8" wall....

The 3 Dirt sides will fall down in No Time,+ your garage Floor is no where Near strong enough...

As noted above,...
It's a Great Idea, but should be built from Above, digging Down,+ building Up...

Building a Vault?

So this is sounding like possible, but yeah, anythign is possible with $$$$$!

OK, how hard would it be to use the existing basement floor and two walls (utilizing a corner) and fabricate two more fireproof walls and a ceiling. Use block? How would I finish the ceiling and attach the walls to the existing concrete?

Building a Vault?

Quote:

Originally Posted by hunt_ak

So this is sounding like possible, but yeah, anythign is possible with $$$$$!

OK, how hard would it be to use the existing basement floor and two walls (utilizing a corner) and fabricate two more fireproof walls and a ceiling. Use block? How would I finish the ceiling and attach the walls to the existing concrete?

I imagine this route would be WAY cheaper....

As stated, you would need to replace the existing garage floor with a re-inforced concrete floor, along with you other plans.

Building a Vault?

How much head room do you have in your basement? You could install load bearing masonry walls for your two partition walls. Depending on the span and other specifics, you could use heavy gauge metal deck as a form and pour a concrete lid. The slab would still need to be reinforced and the metal deck would probably need to be shored before it's poured. Then there's the other aspect of having to get all that stuff into the basement.

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Building a Vault?

FWIW - There are companies that sell pre-fab vaults: walls and ceiling sections that are pieced and attached together. Some of these companies have hollow steel walls that are designed to be filled with concrete after installation. The "resistant material" ceiling panels are then installed.

You could look into these too. I think they start at about $20K.

Just realize that if you are intending to create a safe room, or a fall-out shelter, that there is alot more involved. There is air exchange, filtering of fresh air, H2O, EMP protection, food storage, independent power source, etc, etc....